The present invention relates to an original holder for a printing plate processing apparatus, comprising a vacuum frame having a glass cover plate with a seal, a gas pressure element supporting the glass cover plate of the original holder against a support of the vacuum frame, and a vacuum line leading to a vacuum pump.
U.S. Pat. No. 4,006,984 discloses an original holder of this type, representing an integral part of a printing plate processing apparatus. Known printing plate processing apparatus comprise a charging station for charging the printing plates prior to exposure, an exposure device for exposing the original to light, an optical imaging device for projecting the image of an original onto the electrostatically charged printing plate, and transporting, developing and drying devices.
By means of the exposure device and of the imaging device, exposure of the whole original page is effected, and an image of the original is projected onto the electrostatically charged printing plate. The original and the printing plate must be positioned in the object or image plane, in order to obtain the predetermined reproduction scale. This is achieved by manually placing the original on a horizontally arranged vacuum frame of an original holder and covering it with a glass plate. Then the vacuum frame is pivoted through an angle of 90.degree. into the vertical exposure position. After the exposure, the original holder is swung back to its horizontal position; the glass plate is opened, and the original is removed and replaced by a new original. After closing of the glass plate, the original holder is again pivoted into the vertical exposure position. During these steps, the printing plate processing apparatus does not work, i.e., its utilization capacity is low.